Wittkampf in his U.S. Pat. Nos. 5,697,377 and 5,983,126, discloses a system for determining the position or location of a catheter in the heart. These patents are incorporated by reference in its entirety herein.
In the Wittkampf system current pulses are applied to orthogonally placed patch electrodes placed on the surface of the patient. These patches are used to create axes specific electric fields inside the patient. The patents teach the delivery of small amplitude low current pulses supplied continuously at three different frequencies, one on each axis. Any measurement electrode placed in these electric fields (for example in the heart) experiences voltages depending on its location between the various patches or surface electrodes on each axis. The voltage on the measurement electrode in the field when referred to a stable positional reference electrode indicates the position of the measurement electrode in the heart with respect to that reference. The three voltages give rise to a location of the measurement electrode in “three space”.
Although the Wittkampf system is both safe and effective there are several sources of error that result in errors in position or electrode location. Principle among these is the respiration artifact. For these reasons there is a need for improved location and navigation methods to improve the functionality of the system for the physician.